Exemplary embodiments of the present invention relates to a foldable log-periodic antenna.
A log-periodic antenna (abbreviation LPDA for log-periodic dipole antenna, also referred to for short as a LogPed or LogPer) is a broadband antenna consisting of a number of dipoles, whose length and separation decrease toward the emission direction. The design of an LPDA is fundamentally known, for example from European Patent Document EP 1 923 955 A1.
LPDAs are used, inter alia, as television receiving antennas, in particular in this case DVB-T, since they can equally operate both in the very high frequency range (VHF) and in the ultrahigh frequency range (UHF), thus allowing a plurality of different frequency ranges or channels to be received by a single antenna. Wide frequency ranges can likewise be transmitted and received by LPDAs for EMC measurement technology. Further fields of use are military and civil radio communication, as well as detection vehicles for locating radio interference.
A further field of application of LPDAs is use as jamming transmitters, so-called jammers. In this case, the jamming transmitter transmits energy in the form of electromagnetic waves in an equivalent form to the transmitter to be jammed, in order to superimpose these waves on the original waves from the enemy transmitter, and thus to jam reception by the receiver.
Operationally, the use of a jammer requires a rapid setting-up and removal time. This requires that the LPDA must also be set up and removed again within a short time, that is to say it must be possible to move the LPDA from a transport position to an operating position and vice versa.
Exemplary embodiments of the present invention provide a foldable log-periodic antenna that can be moved from a transport position to an operating position and vice versa.
The log-periodic antenna according to the invention comprises a feed line, one or more transmitting means for transmitting and/or receiving electromagnetic signals, one or more supporting elements for holding the transmitting means, one or more means for producing a tensile stress on the transmitting means. The transmitting means are in this case connected to one of the supporting elements and to the feed line. One supporting element is in turn connected to the feed line via an articulated joint apparatus, such that the antenna can be moved from a transport position to an operating position and vice versa. According to the invention, the one or more means for producing a tensile stress on the transmitting means are in the form of a flexible tube, and can have an internal pressure applied to them. Furthermore, these one or more means for producing a tensile stress on the transmitting means are connected to the supporting elements for holding the transmitting means.
If an internal pressure is applied to the means, which are in the form of a flexible tube, for producing a tensile stress on the transmitting means, for example an internal pressure of up to 50 bar, then they attempt to assume the best energy state. The LPDA is then in the operating state in this best energy state. If the internal pressure is reduced, for example when the antenna is removed, then this best energy state no longer exists, and the antenna can be moved to a transport position.
Since the supporting elements are connected to the means, which are in the form of a flexible tube, for producing a tensile stress on the transmitting means, the antenna is virtually automatically moved from a transport position to an operating position when pressure is applied to the means which are in the form of a flexible tube.
Internal pressure is applied to the means in the form of a flexible tube by options that are known by a person skilled in the art, for example using pneumatic oils or compressed air. The means which are in the form of a flexible tube may, for example, be manufactured from PU flexible tubing or some other flexible and pressure-resistant material which is known by a person skilled in the art.
In a first embodiment of the invention, the transmitting means are in the form of stiff transmitting elements or flexible transmitting braids. Furthermore, the transmitting means are expediently manufactured from a corrosion-resistant conductive material, for example stainless steel.
In a second embodiment of the invention, the supporting elements for holding the transmitting means are in the form of stiff or flexible supporting elements. Expediently, the supporting elements are manufactured from a nonconductive material, for example glass fiber-reinforced plastics.
In a third embodiment of the invention, one or more additional means for producing a tensile stress on the transmitting means, for example one or more spring elements, is or are provided between the supporting element and the transmitting means, and/or between the feed line and the transmitting means. This ensures that a uniform tensile stress acts on the transmitting means despite changes in the length of the transmitting means caused, for example, by temperature fluctuations.